Process Custom Form Data

I’m relatively new to WordPress, but so far I love what it can do! One thing I’m extremely frustrated with is trying to figure out how to handle form data. I don’t like using plugins to create forms, because I like customizing my forms with JavaScript and CSS. However, I would love it if there was a simple way I could send my form data to be saved in the database, and called for in my template with an API. The concept seems so simple, yet after searching and searching, I haven’t found a single plugin or tutorial that does this. I just want my readers to post information into my custom forms, and have the information go into a database. Is there any simple solution for this?